Process for the production of an insulating-coating on electrical conductors.



J. LOEWENTHAL. 4 PROCESS FOR THE PRODUCTION OF AN INSULATING COATING 0NELECTRICAL CONDUCTORS.

APPLICATION FILED 16I 1912.

1,069, 1 5 1 Patented Aug. 5, 1913.

In van/"01,

' o Louwenihal winced/ca I Afr/01 To all whom. it may concern:

Be it known that i, JACQUES LoEwnN-' U D STATES. PATENT FFICE-vJag-icons nonwnnrnanor BERLIN, GERMANY;

' rnocnss 103 min Pnonoc'non THAL, citizen of Germany, subject of theKin of Prussia and Emperor of Germany, resi ing at 137 Grosse.Frankfurterstrasse, Berlin, in the Kingdom of Prussia and Empire ofGermany, have invented new and useful Improvements in Processes for theProduction of an Insulating-Coatin ing is a specification- As is wellknown solutions of aluminium sulating layer. To this end the conductoris treated electrolytically as negative electrode in a bath containingaluminium salt. By suitably selecting the composition of the bath andthecurrent used a firmly adhering coating of aluminium compoundsparticularly of aluminium hydroxidand forming a sound and fire proofinsulator is obtained on the conductor. vThe aluminium hydroxid can beconverted into aluminium oxid by the actionof heat- The accompanyingdrawing represents a diagrammatic view of a device for carrying out theprocess according to this invention.

For the purpose of carrying the process into effect solutions ofaluminium salts may be used such as are for instance described in thescientific literature more especially in connection with the analyticalseparation of aluminiumin the form of hydroxid. A suitable bath is forexample that suggested by A. Classen and consisting of a solution ofaluminium-ammonium oxalate with an excess of ammonium oxalate. From thisbath the aluminium is precipitated on the cathode in the form'ofhydroxid under the action of the current to the extent to which theammonium oxalate is converted into ammonium carbonate. For practicalpurposes for example an aqueous or slightly acidulated solution ofaluminium sulfate neutralized if desired by means of ammonia is treatedwith an excess of ammonium oxalate, adding with the application of heat,if

on Electrical Conductors, of which the 0 low or s msonnrr'nc-coa'rme onnnnernrcnr. connocrons,

I Specification otletters Patent. Patented Aug, 5,1913, Applicationiiled'necemhcr 16, 1912.; Serial No. 737,097. a I

desired, gsolid ammoniumoxalate so that two to three gramsammoniumoxalate are. used for each 0.1 glf. of the metal. The strength of thecurrent is so chosen as to roduoe a violent decomposition of the oxa icdouble salt. The conductor thoroughly cleaned is immersed in this bathand used as a cathode, the anode consistin ofany desired conductivesubstance whic is not attacked by the liquid of the bath such asplatinum. The shape ofthe anode is by preference as nearly as ossiblethat of the conductor so that the dlstance between all points of thesurface of the conductor and the nearest point of the anode is the sameas nearly as possible. From this bath the aluminium is precipitated inthe form of hydroxid which very firmly adheres to the conductor.

An exceedingly suitable example for treating sheet metal or metal wiresuch as copper wire or copper band, is as follows:

The metal such as copper sheet or copper wire to be coated withaluminium oxid is I first of all carefully cleaned by the removal of thefatty layer adhering to it. This is efiectedby means of benzol, ammonia,spirit or the like and subsequently etching it with acid or othercorrosives'. By 'pre'fe'rendo the etching is effected electrolyticallyby" added. The quantity of nitrate of mercury added may for instance besuch that the contents thereof in the solution amount to about 0.1%,fresh mercury salt. being added from time to time. In this bath thecopper body forms the cathode and the anode is made to annularlysurround the same. For the anode lead with lead-peroxid is preferablyused. This may be obtained by treating lead sheets as anode in sulfuricacid of about 25% with lOO moderately strong current for sometime. Inthe bath of the aluminium salt the a'luminium oxid or hydroxid is nowprecipitated on the copper. Good results can be obtained with a terminaltension of 24: volts and with a current density at the cathode of atleast 0.1 to 0.5 ampcres per square centimeter surface. in order toincrease the firm adhesion of the precipitate the liquid is stronglyagitated during the action. This may conveniently be cll'ected byblowing in air between the anode and cathode for instance with the aidof a pipe extending into the interior of the annular anode. This pipemay consist of nouronductivc material and for the treatment of wire orband may simultaneously serve as a guide for these bodies. After theelectrolytic treatment which may be complotcd in about half a minute thecopper body is rinsed and then heated to drying without glowing. Ifafter one treatment there are still places to which the precipitate doesnot firmly adhere the treatment can be repeated with absolute success,the cause for the non-adhesion being in most cases due .to the coppernot having been entirely freed from fat or like layers at the outset. Adevice by means of which for instance copper wire may be coated withhydroxid of aluminium in a .continuous manner is diagrammaticallyillustrated in the accompanying drawing. The copper wire a is firstdrawn through the caustic bath b and then through the electrolytic bath0. In the former bath the wire a forms the anode and in the latter it isused as cathode. In the caustic bath the wire is surrounded by theannular cathode (1 consisting for instance of copper and in theelectrolytic bath it is surrounded by the anode 6 consisting forinstance of lead with lead-peroxid. For guiding the wire a tube f g h isused which may simultaneously serve as a means for blowing in air intothe space between the anode and cathode in the bath. The admission ofair may be eilec-ted for instance at the points g h by way of suitablenozzles or the like. In the rear of the electrolytic bath a the wire isbrought .into suitable washing devices in which it is freed from theadhering hath liquid and then into drying apparatus consisting forinstance of a gas oven in which the wire is heated without being causedto glow, and finally on to winding apparatus for the formation of spoolsor the like.

Mercury salts are employed because it has been found that the aluminiumoxid is precipitated in a more complete and in a much quicker mannerfrom the bath when the mercury salt is added than when the bath is usedwithout it. The use of lead with lead peroxid as an'anode isadvantageous as this material is not affected by the solutions appliedand is cheaper than any other resistant conducting material such as thenoble metals.

Having now described my invention what I claim and desire to securebyLetters Patent of the United States is:

1. A process for the production of an insulating coating on electricalconductors consisting in the precipitation electrolytically on theconductor used as a cathode of strongly adhering aluminium compoundsfrom a suitable solution of aluminium salts.

2. A process for the production of an insulating coating on electricalconductors consisting in the precipitation electrolytically on theconductor used as a cathode of strongly adhering aluminium compounds.

from a suitable solution of aluminium salts with an addition of mercurysalts.

3. A process for the production of an insulating coating on electricalconductors consisting in the precipitation electrolytically on theconductor used as a cathode of strongly adhering aluminium compoundsfrom a suitable solution of aluminium salts, thedanode consisting oflead with lead-per- 0X1 4. A process for the production of an insulatingcoating on electrical conductors consisting in cleaning the saidconductor by removing the fatty layer adhering to it and subsequentlyetching it then bringing it as cathode into an electrolytic bathconsisting.

of a solution of aluminium acetate containing nitrate of mercury andsubjecting it to an electrical current, the anode consisting of leadwith lead-peroxid and finally rinsing and drying said conductor.

5. A process for the production of an insulating coating on electricalconductors consisting in the precipitation electrolytically on theconductor used as a cathode of strongly adhering aluminium compoundsfrom a suitable solution of aluminium salts subjecting the liquid tostrong agitation during the precipitation of the aluminium compoundspreferably by blowing in air between the anode and cathode. I

6. A process for the production of an insulating coating on electricalconductors consisting in the precipitation electrolytically on theconductor used as a cathode of strongly adhering aluminium compoundsfrom a suitable solution of aluminium salts subjecting the liquid tostrong agitation during the precipitation of the aluminium compoundspreferably by blowing in air between the anode and cathode through apipe, which is simultaneously used as a guide for the conductor such ascopper wire to be coated with aluminium hydroxid.

7. A process of producing an insulating coating on electrical conductorswhich con-' Y 8. A process of insulating electrical con-- ductors whichconsists in electrolytically depositing on said conductors aluminiumoxid from a solution containing aluminium salt.

9. A process of insulating electrical conductors which consists inelectrolytically depositing on said conductors aluminium oxid from asolution containing aluminium salt, said solution being free of othermetals which are electrolytically deposited in a metallic state.

10. A process of insulating electrical conductors which consists inelectrolytically depositing on said conductors aluminium oxid from asolution containing aluminium salt, said solution being free of iron.

11. A process of insulating electrical conductors consisting inelectrolytically depositin aluminium oxid from a solution containingaluminium salt on said conductors and employing'a current of a strengthsufficient to cause the aluminium oxid precipitated to firmly adhere tothe conductor.

12. A process of insulating electrical conductors consisting inelectrolytically depositing aluminium oXid from a solution containingaluminium salt on said conductors and employing a current of a strengthsufficient to cause the aluminium oxid precipitated to firmly adhere tothe conductor. said current having a terminal tension of more thantwenty volts.

13. A process of insulating electrical conductors which consists inelectrolytically depositing on said conductors aluminium oxid from asolution containing aluminium salt and moving said conductor through thebath during the electrolytical treatment.

In testimony whereof I have hereunto set my hand in presence of twosubscribing witnesses.

JACQUES LOE-lVENTHAL. Witnesses:

lVALDEMAR HAUPT, HENRY HASPER.

